The bitcoin network is a peer-to-peer payment network that operates on a cryptographic protocol. Users send and receive bitcoins, the units of currency, by broadcasting digitally signed messages to the network using bitcoin cryptocurrency wallet software. Transactions are recorded into a distributed, replicated public database known as the blockchain, with consensus achieved by a proof-of-work system called mining. Satoshi Nakamoto, the designer of bitcoin claimed that design and coding of bitcoin began in 2007. The project was released in 2009 as open source software. The network requires the minimal structure to share transactions. An ad hoc decentralized network of volunteers is sufficient. Messages are broadcast on a best effort basis, and nodes can leave and rejoin the network at will. Upon reconnection, a node downloads and verifies new blocks from other nodes to complete its local copy of the blockchain. A bitcoin is defined by a sequence of digitally signed transactions that began with the bitcoin's creation, as a block reward. The owner of a bitcoin transfers it by digitally signing it over to the next owner using a bitcoin transaction, much like endorsing a traditional bank check. A payee can examine each previous transaction to verify the chain of ownership. Unlike traditional check endorsements, bitcoin transactions are irreversible, which eliminates the risk of chargeback fraud. Although it is possible to handle bitcoins individually, it would be unwieldy to require a separate transaction for every bitcoin in a transaction. Transactions are therefore allowed to contain multiple inputs and outputs, allowing bitcoins to be split and combined. Common transactions will have either a single input from a larger previous transaction or multiple inputs combining smaller amounts, and one or two outputs: one for the payment, and one returning the change, if any, to the sender. Any difference between the total input and output amounts of a transaction goes to miners as a transaction fee. In 2013, Mark Gimein estimated electricity consumption to be about 40.9 megawatts (982 megawatt-hours a day). In 2014, Hass McCook estimated 80.7 megawatts (80,666 kW). As of 2015, The Economist estimated that even if all miners used modern facilities, the combined electricity consumption would be 166.7 megawatts (1.46 terawatt-hours per year). To lower the costs, bitcoin miners have set up in places like Iceland where geothermal energy is cheap and cooling Arctic air is free. Chinese bitcoin miners are known to use hydroelectric power in Tibet to reduce electricity costs. Various potential attacks on the bitcoin network and its use as a payment system, real or theoretical, have been considered. The bitcoin protocol includes several features that protect it against some of those attacks, such as unauthorized spending, double spending, forging bitcoins, and tampering with the blockchain. Other attacks, such as theft of private keys, require due care by users.
Bytecoin is the first cryptocurrency created with CryptoNote technology. Bytecoin allows users to make absolutely anonymous money transfers through the CryptoNote algorithm. CryptoNote uses CryptoNote ring signatures to provide anonymous transactions and allows you to sign a message on behalf of a group. The signature only proves the message was created by someone from the group, but all the possible signers are indistinguishable from each other. Even if outgoing transactions are untraceable, everyone may still be able to see the payments received and thus determine one's income. By using a variation of the Diffie-Hellman exchange protocol, a receiver has multiple unique one-time addresses derived from his single public key. After funds are sent to these addresses they can only be redeemed by the receiver; and it would be impossible to cross-link these payments. As a primarily peer-to-peer (p2p) payment system, Bytecoin has many of the same use-cases as Bitcoin. Created in 2012, Bytecoin is one of the earliest developed cryptocurrencies. Until recently, the team behind the coin has kept themselves anonymous. Now, though, they’ve opened up multiple communication channels, removed some layers of anonymity, and even built several local communities. Bitcoin’s PoW consensus algorithm heavily favors miners that use powerful GPU and ASIC machines over those trying to mine with CPUs. This causes the network to centralize around the more powerful miners. Bytecoin attempts to close the gap between these two classes of miners with a new algorithm, Egalitarian Proof-of-Work (PoW). Egalitarian PoW uses a version of skrypt, a proof of work function similar to the hashcash function used by Bitcoin. The difference between the two is that scrypt isn’t memory bound. Because of this, you can produce highly efficient CPU mining rigs. GPUs will always be about 10 times more effective, though. The Bytecoin project has been fairly fractured since its inception in July 2012. Previously, several isolated teams worked on the project without seemingly communicating with each other. This led to numerous forks and versions of the coin. In July 2017, the team decided to change their image and provide more transparency to the community. The team still remains pseudo-anonymous by only providing names and headshots on their webpage – no bios or social media links. But, it’s tough to expect more from a project that’s focused on privacy. The team has been busy at work refactoring their code and are planning to release a new public API on February 6, 2018. They’ll also be entering the Asian, Middle East, and African markets throughout 2018.